Evidence for Nanoparticle-Induced Lysosomal Dysfunction in Lung Adenocarcinoma (A549) Cells.

Arnold Sipos,Constantinos Sioutas,Edward D. Crandall,Kwang-Jin Kim

doi:10.3390/ijms20215253

Abstract

Background: Polystyrene nanoparticles (PNP) are taken up by primary rat alveolar epithelial cell monolayers (RAECM) in a time-, dose-, and size-dependent manner without involving endocytosis. Internalized PNP in RAECM activate autophagy, are delivered to lysosomes, and undergo [Ca2+]-dependent exocytosis. In this study, we explored nanoparticle (NP) interactions with A549 cells. Methods: After exposure to PNP or ambient pollution particles (PM0.2), live single A549 cells were studied using confocal laser scanning microscopy. PNP uptake and egress were investigated and activation of autophagy was confirmed by immunolabeling with LC3-II and LC3-GFP transduction/colocalization with PNP. Mitochondrial membrane potential, mitophagy, and lysosomal membrane permeability (LMP) were assessed in the presence/absence of apical nanoparticle (NP) exposure. Results: PNP uptake into A549 cells decreased in the presence of cytochalasin D, an inhibitor of macropinocytosis. PNP egress was not affected by increased cytosolic [Ca2+]. Autophagy activation was indicated by increased LC3 expression and LC3-GFP colocalization with PNP. Increased LMP was observed following PNP or PM0.2 exposure. Mitochondrial membrane potential was unchanged and mitophagy was not detected after NP exposure. Conclusions: Interactions between NP and A549 cells involve complex cellular processes leading to lysosomal dysfunction, which may provide opportunities for improved nanoparticle-based therapeutic approaches to lung cancer management.

Highlights

Nanoparticle (NP) exposure has been reported to induce stress in various cells and tissues [1,2,3,4]
We found that apical NP exposure of A549 cells leads to activation of autophagy and increased lysosomal membrane permeability (LMP) without mitochondrial dysfunction
Using a live cell imaging approach, we demonstrated that polystyrene nanoparticles (PNP) are taken up into A549 cells, at least in part by macropinocytosis

Summary

Introduction

Nanoparticle (NP) exposure has been reported to induce stress in various cells and tissues [1,2,3,4]. Following internalization of foreign materials (e.g., proteins, bacteria, virus and (nano)particles), autophagy is activated as part of cellular defense mechanism(s) [13]. Polystyrene nanoparticles (PNP) are taken up by primary rat alveolar epithelial cell monolayers (RAECM) in a time-, dose-, and size-dependent manner without involving endocytosis. Internalized PNP in RAECM activate autophagy, are delivered to lysosomes, and undergo [Ca2+]-dependent exocytosis. Mitochondrial membrane potential, mitophagy, and lysosomal membrane permeability (LMP) were assessed in the presence/absence of apical nanoparticle (NP) exposure. Conclusions: Interactions between NP and A549 cells involve complex cellular processes leading to lysosomal dysfunction, which may provide opportunities for improved nanoparticle-based therapeutic approaches to lung cancer management

Methods

Discussion

Conclusion